The experiments described in this proposal are concerned with the extent to which gonadal hormones modulate appetitively motivated learned behavior. The specific aims of the research are centered around answering three questions: (1) to what extent do male and female gonadal hormones alter appetitively motivated behavior, (2) to what extent are the modulatory effects of gonadal and pituitary-adrenal hormones interdependent, and (3) what is the neural locus of the modulatory effect of testosterone. With respect to the first question, we propose to determine: (a) whether our previous findings of gender differences in appetitively motivated behavior are due to organizational or activational effects of testosterone, (b) whether androgenic or estrogenic pathways of testosterone metabolism are involved, and (c) whether female gonadal hormones are also behaviorally active. With respect to the second question, we propose to determine: (a) whether ACTH modulation of appetitive extinction behavior is absent in castrated males and in females, (b) what part of the ACTH peptide sequence is active, (c) whether the behavioral gender differences can be attributed to known gender differences in tonic and dynamic pituitary-adrenal hormones, or (d) are the effects of pituitary-adrenal and gonadal hormones acting interdependently. With the information obtained by answering the first two questions and the known distribution of receptors for male and female hormones and their metabolites, we will be in a position to start an investigation of the third question -- what is the neural locus of the modulatory effects of gonadal hormones. The long term goals of our research are to increase the knowledge about the non-reproductive effects of gonadal hormones and to determine the mechanisms that are involved.